This application claims a priority based on Japanese Patent Application No. 11-335148 filed on Nov. 25, 1999, the entire contents of which are incorporated herein by reference for all purpose.
As shown in FIG. 1, a background of an animation of a video game or the like is generated by mapping a rendering image of a three-dimensional background scene over a virtual plane 501. A virtual viewing camera 500 is defined for the virtual plane 501. A visible region 503 or 502 that is clipped by the visual field of the viewing camera 500 is regularly subjected to rendering on the display screen of a display device. If the direction of the viewing camera 500 is changed in accordance with an input from a user, a resulting front view is displayed on the display screen of the display device in real time.
However, since a rendering image of a three-dimensional background scene is mapped over the virtual plane 501, an image on the display screen may be distorted depending on the direction of the viewing camera 500. That is, if the front side of the viewing camera 500 is directed squarely to the model plane 501 (direction (a) in FIG. 1), a proper image 503 without distortion is displayed on the display screen. However, if the viewing camera 500 is panned rightward, leftward, upward, or downward (direction (b) in FIG. 1), an image 502 whose peripheral region is distorted is displayed on the display screen.
Further, if a close-range view is included in a three-dimensional scene for generation of a rendering image to be mapped over the virtual plane 501, when, for example, the viewing camera 500 is panned, there may occur a case that a close-range-view image on the display screen is out of perspective and hence the image on the display screen seems unnatural. For this reason, usually, the above-described background image generation technique is applied to only a distant view.
The present invention relates to a computer graphics technique that is used for generation of an animation of a video game or the like. An object of the present invention is to make it possible to display a high-quality background image that is free of distortion due to a pan of a viewing camera in a 3D-CG animation.
To attain the above object, the invention provides an entertainment apparatus which operates, in accordance with an input from a controller, a subject model of operation displayed on a display screen, comprising moving image control means for moving the subject model of operation disposed inside a virtual first sphere within a predetermined moving range in accordance with an input from the controller, and for rotating a virtual viewing camera located at the center of the sphere model in accordance with the movement of the subject model of operation; and rendering means for rendering, from the virtual viewing camera, on the display screen, a model included in a region that is clipped by a visual field of the virtual viewing camera as the viewing camera is rotated, wherein a rendering image produced by rendering of a three-dimensional background scene is mapped over an inside surface of the first sphere.
It is desirable that the xe2x80x9crendering image produced by rendering of a three-dimensional background scenexe2x80x9d be an image produced by (1) projecting a three-dimensional background scene onto the inside surface of a virtual sphere from a viewing point that is located at the center of a virtual sphere having the same shape as the first sphere over which the image is to be mapped, or (2) finally connecting a plurality of rendering images obtained by rotating a viewing camera defined at a prescribed position so that they are located around a virtual sphere.
In the above entertainment apparatus, a rendering image of a three-dimensional background scene is mapped to the inside surface of a virtual sphere and a viewing camera is defined at the center of the first sphere. Therefore, even if the viewing camera is panned leftward or rightward, no distortion occurs in a peripheral region of a background image on the display screen.
Even if a rendering image includes both of a close-range view and a distant view, a pan of the viewing camera in any direction does not impair the perspective of a display image on the display screen because the distance between the front side of the viewing camera and the rendering image is kept constant. Since the moving range of a subject model of operation is restricted, even if a rendering image includes a close-range view, there does not occur a case that an unnatural image such as an image in which an object as a subject of operation passes through the close-range view is displayed on the display screen.
Each means of the above entertainment apparatus may be realized by either hardware or software.